A chimpanzee had to get stiches after attempting to gnaw off his own arm in a drug-fuelled psychosis.
A family told keepers at Dyreparken Zoo and Amusement Park in Norway they had seen someone throw a bottle into the enclosure.
Keepers grew concerned when their 39-year-old chimp began behaving strangely. After checking CCTV, the keepers saw Julius - who loves sweet, fizzy drinks - carrying the bottle, reports The Daily Mail.
He then began to act strangely, sitting by himself, and biting his arm.
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Vets tranquilised Julius, so they could treat his arm, as they feared he had broken it. However, they only found self-inflicted bite wounds, which required stitches.
After another operation to re-treat his wound the following day, Julius seemed to be on the mend.
Zoo workers sent off samples of his blood and urine to a nearby hospital, which confirmed he had unspecified narcotics in his blood.
Keepers wrote on the zoo's website they were "shocked" something like this had happened.
"We're so glad he's getting better, and his wound is healing. It could have been so much worse," wrote Rolf-Arne Olberg, the zoo's veterinarian.
Julius is the only chimp in the zoo that is able to unscrew bottle tops, and keepers have passed the CCTV footage of the bottle being tossed into his enclosure on to police, in the hope they can find out who drugged Julius.